In modern technical systems, for example industrial production systems and assembly lines, transport and conveying systems, operating cycles are increasingly controlled by automation. These types of systems have a central operation controller, which receives setpoint and process values from the system and, based on these, uses a control program implemented in the operation controller to generate corresponding control signals by which the actuators of the system may be actuated.
In addition to the control of the actual operating cycle of the technical system, safety aspects also play an important role. In this context, it concerns preventing hazards which arise from the individual system component groups from affecting humans who are in the vicinity of these system component groups. For example, system component groups, which may execute automated movements, are protected by suitable protective barriers, light barriers, tread mats, and the like. Furthermore, to protect people, protective doors, protective flaps, and the like may be used, which comprise an actuator/sensor combination, by which an opening process may be reliably detected so that the entire system or at least one dangerous system component of the system may be shutdown or transitioned into a state that is not hazardous for humans. In addition, it is also known to equip technical systems with emergency off or emergency stop buttons/switches, due to the actuation of which, the entire system, or at least one of the dangerous system components of the system, may be shut down, or transitioned in another way into a state that is not hazardous for humans. For this purpose, corresponding safety circuits are used in the prior art, as they are known, for example, from EP 1 363 306 A2 or DE 10 2004 020 995 A1.
In assembly lines, it is often necessary that multiple safety switching devices, which monitor individual dangerous system component groups and initiate, in the event of danger, a reliable shutdown process of the relevant system component group or transition this system component group into an operating state that is not hazardous to humans, are connected to one another. One objective during the design layout of the individual safety switch devices consists in that all system component groups connected thereto simultaneously shut down when an emergency off or emergency stop button/switch is actuated at one of the system component groups. Faults in the connecting wiring of the safety switching devices among themselves, or in the safety switching devices themselves, are thereby not permitted to lead to a loss of these safety functions or to a dangerous operating state of the entire system or to individual system component groups.
In the prior art, the individual safety switching devices were, for example, connected to one another via a secure data bus or by conventional wiring of multichannel inputs and outputs of the safety switching devices to one another. This is linked to relatively high effort and subsequently also to high costs.
In safety switching devices, which are operated by the applicant under the designation “PNOZ®elog”, a star-shaped cascading is provided by a pulse signal to an information transmission line. Information, in particular a reliable shutdown message, may thereby be transmitted by a transmitter via the information transmission line in only one specific information flow direction. In other words, this means that the information is transmitted from a transmitter in a specific information flow direction and is received by one or more receivers.